In the known liquid crystal displays (LCDs), white light emitting diodes (LEDs) are usually used as the backlight light source. Appropriate configuration of the light guide plate and the optical film can achieve the required backlight. Currently, the people's demand of high color gamut, high color saturation, and energy saving LCDs is increasing. Several techniques, for example, ultraviolet LEDs with red, green and blue florescent powder, or blue LEDs with red and green florescent powder, or blue LEDs with green LEDs and red LEDs, can achieve the white light source required by backlight of such LCDs. These techniques can increase the color gamut, however it is difficult to implement and the cost is also high.
Quantum dots (QD) is a type of semiconductor structure that is capable of restraining electrons within a certain range. Quantum dots usually consist of ultrafine compound crystals having a diameter of 1˜100 nm. Quantum dots can control the wavelength of the light using the size of the crystals, thereby controlling the color of the light. Thus, quantum dots material is used in the backlight, the high frequency light source (i.e., blue LEDs) is used to replace the conventional white LEDs. The irradiation of quantum dots at the high frequency is low and can produce light of different wavelength after being irradiated by laser. By adjusting the size of the quantum dots material, the color the light mixed can be adjusted, and thus the backlight requirements of high color gamut LCDs is achieved.
FIG. 1 is a schematic view of a known backlight module using the quantum dots florescent powder film. As shown in FIG. 1, a blue LED 11 is disposed at a light incident side surface of a light guide plate 12, a quantum dots florescent powder film 13 is disposed at a light emitting surface of the light guide plate 12. The light emitted by the blue LED 11 is converted to surface light by the light guide plate 12, and is emitted from the light emitting surface of the light guide plate 12, then the light passing through the florescent powder film 13 is converted into the light source required by a LCD. However, in big-size LCDs, the area of the quantum dots florescent powder film 13 has is also very big, and thus a lot of quantum dots material is required. In addition, the florescent powder coating is also required to be very uniform, and therefore the cost is very high. Besides, if the optical film has a different configuration or a different model, the light after being processed by the optical film will have quite different color tone and brightness. Thus, the configuration, the supplier and the mode of the optical film shouldn't be easily changed during the using of the quantum dots florescent powder 13, and this significantly limits the flexibility and universality of quantum dots florescent powder film.
FIG. 2 is a schematic view of a known backlight module using the quantum dots florescent powder film. Referring to FIG. 2, a blue LED 21 is disposed at a light incident side surface of a light guide plate 22, quantum dots florescent powder is packaged in a glass tube to form a quantum dots florescent powder glass tube 23. The quantum dots florescent powder glass tube 23 is disposed between the blue LED 21 and the light incident surface of the light guide plate 22. The light emitted by the blue LED 21 passes through the quantum dots florescent powder glass tube 23 and irradiated the light incident surface of the light guide plate 22. However, it is complicated to manufacture the quantum dots florescent powder glass tube 23 and the cost is high, and the quantum dots florescent powder glass tube 23 is easily broken.